forjonathanwilson (7/21/2010)

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A calculated field is not going to be A+B, because thats just a stupid test case. More likely a computed field will be connected to a UDF and be gathering data from elsewhere.

jghali (7/21/2010)

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We use them here for Total Calculations using UDF functions.
But since we are developping the application, we are beeing very careful that they are only used when there aren't too many columns returned...

wware (7/21/2010)

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Not in my experience! Computed columns are often used in data warehousing for mundane things like FullName and Age, two examples mentioned by others in this discussion.

jghali (7/21/2010)

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Sorry about the ambiguous answer.

What I was trying to get to is...

Retrieving data from a normal column is much faster then having to calculate the value every time a computed field is called.
Can you imagine, if you are calling 100 000 rows including a computed column? It would definitely take more resources specially if the computed column comes from other tables via UDFs...

CREATE TABLE Demo
   (KeyCol int NOT NULL PRIMARY KEY,
    SmallString varchar(10) NOT NULL,
    Repetitions smallint NOT NULL,
    LongString AS REPLICATE(SmallString, Repetitions));